Process of hardening epoxy coating composition with dicyandiamide/imidazoline derivative

Abstract

An improvement for producing a coating from a powder lacquers composition comprising at least one 1,2-epoxide compound having at least one 1,2-epoxide group in the molecule which compound has a lower melting point greater than 40° C., and dicyandiamide wherein the powder coating lacquer composition additionally contains an imidazoline derivative of the general structure ##STR1## wherein R is hydrogen, an alkyl or aryl residue, R' is a cycloalkyl, heterocyclo alkyl or R, R" is an alkyl or aryl substituted or unsubstituted alkylene or arylene, X is hydrogen or a radical having the following structure ##STR2##

What is claimed is: 
     
       1. In a process for producing a coating of a powder lacquer composition wherein a powder lacquer composition is applied to a substrate, the powder lacquer composition comprising a finely particulate mixture of a 1,2-epoxide compound, which epoxide compound contains at least one 1,2-epoxide group in the molecule and has a lower melting point greater than 40° C., and dicyandiamide the improvement which comprises including in the composition at least one imidazoline derivative of the general structure ##STR5## wherein R is hydrogen, an alkyl or aryl, R' is a cycloalkyl, heterocyclo alkyl or R, R" is an alkyl or aryl substituted or unsubstituted alkylene or arylene , X is hydrogen or a radical having the following structure ##STR6## the dicyandiamide being present in excess relative to said imidazoline. 
     
     
       2. A process according to claim 1 wherein the imidazoline derivative is selected from the group consisting of 2-methyl-imidazoline, 2,4-dimethyl-imidazoline, 2-chloromethyl-imidazoline, 2-ethyl-imidazoline, 2-ethyl-4-methyl-imidazoline, 1-vinyl-2-methyl-imidazoline, 2-benzyl-imidazoline, 2-(1-naphthyl-methyl)-imidazoline, 2-phenyl-4-methyl-imidazoline, 2-(o-tolyl)-imidazoline, 2-(m-tolyl)-imidazoline, 2-(m-tolyl)-4-methyl-imidazoline, 2-(p-tolyl)-imidazoline, 2-(m-pyridyl)-imidazoline, 2-(p-pyridyl)-imidazoline, tetramethylene-bis-imidazoline, 1,4-tetramethylene-bis-(4-methyl-imidazoline-2), 1,1,3-trimethyl-1,4-tetramethylene-bis-imidazoline, 1,3,3-trimethyl-1,4-tetramethylene-bis-4-methylimidazoline, 1,2-phenylene-bis-imidazoline, 1,3-phenylene-bis-imidazoline, 1,4-phenylene-bis-imidazoline, and 1,4-phenyl-bis-4-methylimidazoline. 
     
     
       3. A process according to claim 1 wherein the mixture of dicyandiamide and imidazoline derivative is employed in an amount of 3.5 to 18 parts by weight per 100 parts by weight of epoxide compound. 
     
     
       4. A process according to claim 1 wherein the mixture of dicyandiamide and imidazoline is employed in a combined amount of 5 to 9 parts by weight per 100 parts by weight of epoxide resin. 
     
     
       5. A process according to claim 1 wherein the 1,2-epoxide compound is a saturated or unsaturated aliphatic, cycloaliphatic, aromatic or heterocyclic, 1,2-epoxide compound. 
     
     
       6. A process according to claim 1 wherein the epoxide compound is a solid polymeric polyglycidyl polyether of 2,2-bis-(4-hydroxyphenyl)-propane. 
     
     
       7. A process according to claim 1 wherein the 1,2-epoxide compound has an epoxide equivalent weight lying between 500 and 1000. 
     
     
       8. A process according to claim 1 wherein the epoxide compound is a solid epoxidized polyester of a low molecular weight polyepoxide selected from the group consisting of diglycidyl ethers of 2,2-bis-(4-hydroxyphenyl)-propane, diglycidyl phthalate, diglycidyl adipate, diglycidyl tetrahydrophthalate, diglycidyl hexahydrophthalate, diglycidyl maleate and 3,4-epoxycyclohexyl methyl ester of 3,4-epoxy-cyclohexane carboxylic acid. 
     
     
       9. A process according to claim 1 wherein the epoxy compound is the polyglycidyl ether of 1,1,2,2-tetra-(hydroxyphenyl)-ethane.